The Obama White House and congressional Democrats headed into the shutdown smackdown Monday night united around Harry Reid’s hardball strategy: no more concessions on the continuing resolution. And no caving on the debt ceiling, either.

The Senate majority leader and other top Democrats have had their issues with the White House in the past — never more so than in the fiscal-cliff deal negotiated by Vice President Joseph R. Biden Jr., which many Democrats felt gave away the store on taxes without reaching a long-term deal on spending.

Not this time, they say with a united voice.

Democrats and the White House could have dug in, too — as House Minority Whip Steny H. Hoyer of Maryland had floated — by demanding more spending than the $986 billion sequester level proposed by the GOP. But the heart of the Reid-White House strategy has been to ask for nothing and try to force Republicans to own a shutdown if it happens. They didn’t demand any new riders or new spending.

They accepted the House’s spending level, even though Democrats preferred the $1.058 trillion pre-sequester target called for in the 2011 Budget Control Act. They agreed to a separate House bill to make sure troops continue to get paid. On the rest of the CR, it’s “clean” or bust.

It’s a strategy that helped Reid line up all 54 senators in his caucus and eventually brought along House Democrats, including Hoyer.

By Monday afternoon, the Democratic mantra was that the Senate’s “clean” CR would pass easily on the House floor — relying on Democratic votes — if only Speaker John A. Boehner would bring it up for a vote.

“If John Boehner blocks this, it would be forcing a government shutdown. And it would be a Republican government shutdown, pure and simple. ... The votes are there to pass a clean CR,” Reid said.

Republicans have been directing their ire in every direction, including at each other, given that many have said shutting down the government over Obamacare is a plan sure to fail.

The easy GOP attack was to slam the president for not bringing the leaders together for a negotiation — especially considering that he had chatted and entertained talks with the president of Iran a few days before.

While Obama said Monday he would speak to congressional leaders, there have been no real talks for weeks and none at the White House.

“He seems absolutely allergic to doing his job,” Sen. John Cornyn, R-Texas, said on the Senate floor, complaining that the president was missing in action.

Rep. Michael C. Burgess, R-Texas, complained that the Senate was not compromising on Obamacare.

“It’s hard to negotiate with someone who doesn’t want to negotiate with you, and that’s the position we’re in right now,” Burgess said.

For Reid and the White House, it’s less about any one provision and more about the precedent that caving would set, knowing full well that a debt ceiling default looms a few weeks away, with a full-year budget negotiation shortly thereafter.

The message from the White House has been twofold and consistent: The president is “eager” to negotiate a budget, but won’t do it under threat of a shutdown or a default.

And Obama, in a statement at the White House late Monday, made it clear that Obamacare would continue forward, no matter what Congress did.

“You can’t shut it down,” he declared.

Democrats, for their part, are pleased for once that the White House hasn’t opened up back-channel negotiations of its own. When that’s happened in the past, Republicans have gotten concessions, sometimes very big ones. When the White House has stuck with Reid, they’ve gotten the House to buckle, Democratic aides said.

“We hope it lasts,” one aide said of the unified position.

Reid, for his part, is sick of negotiating on Republican terms.

“We are not going to negotiate on this,” the Nevada Democrat insisted Monday afternoon.

“Democrats are through negotiating with ourselves,” he added later. “Why they can’t take ‘yes’ for an answer is hard for me to understand.”

Reid said the president’s meetings with Republicans have never borne fruit.

“The president has met with these folks all over town, the White House, took them to dinner at fancy restaurants. He put in writing what he was willing to do — put in writing,” Reid said. “They have yet to issue a sentence after all those meals, not a sentence as to what they’re willing to do, which is nothing. So our negotiation is over with, and I have said that for two weeks.”

Democrats made clear they were just as worried, if not more so, about the debt ceiling fight to follow.

“If we give an inch on the CR, the hard right will say, ‘See they gave in, let’s demand more,’” Sen. Charles E. Schumer told reporters Monday. “We won’t be extorted now. We won’t be extorted two weeks from now. We won’t be extorted in December.”

Republicans kept floating new ideas for concessions they hoped to extract as a condition for keeping the government open.

By midday Monday, Republicans were floating the idea of a one-week CR — a proposal Reid quickly dismissed. Asked about a one-week, a three-day or even a one-day continuing resolution, the former boxer was in fight mode.